Present commercially available baby bouncer apparatus generally comprises means for clamping over a door lintel, such as slidably or pivotally connected jaw elements, or else a ceiling mounted hook, and, attached thereto, optionally by way of a non-extensible connector, such as a chain, an elongate tension spring, usually a helical spring, but occasionally a strip of rubber or the like, which in use is arranged vertically and is extensible vertically, in the direction in which load is applied. Attached to the other end of the spring, again optionally by way of an inextensible connector, is a transverse bar, from the extremities of which, a harness for the baby is suspended by way of respective lines, such as cords, ropes or chains. The harness generally comprises a portion which fits between the baby's legs and a portion which fits around his/her waist. It may be relatively rigid, in the manner of a seat, or relatively flexible, in the manner of a belt, with a looped lower piece to fit between the legs.
In use, the bouncer apparatus should be so arranged that the baby, when seated or strapped into the harness, is able to stand with his/her feet in contact with the ground, but the suspension means should be of such length and the spring of such tension, that, at rest, the baby is properly supported and is not in a position of having bent knees with feet flat on the ground. The baby should then be able to exert positive downward force by bending his/her legs so as to extend the spring, which will then react, when that force is released, by reducing in length and permitting upward bouncing of the baby. In this respect, it will be appreciated that the purpose of the apparatus, in addition to providing an enjoyable activity for the baby, while it is safely retained (i.e. incapable of crawling about with all the risks that involves), is to develop the strength of the baby's legs, as well as general co-ordination in an upright position as a precursor to walking.
Problems can arise in three areas in relation to the known commercial baby bouncers. Firstly, in respect of the overhead fixing, clamping may not be sufficiently secure, particularly if the lintel does not provide a wide ledge to engage over, and the alternative of a hook means a permanent fixing position, and a permanent fixture, which cannot be removed without repair being necessary. Secondly, the tension of the spring is critical to satisfactory operation of the bouncer, and this may prove inadequate, or start to fail after prolonged use. Thirdly, and this is connected also to the matter of spring tension, the height available between the overhead fixing (lintel or ceiling hook) and the harness may often prove inadequate, and this puts constraints on the spring, which then cannot be too long and must have a relatively high co-efficient of tension (elasticity).